Catalytic processes for the hydrogenation of aliphatic and aromatic nitriles to produce a product slate rich in primary amines and the subsequent conversion, disproportionation of the primary amines to produce secondary amines are known. The product slate obtained by the hydrogenation of the nitriles may range from primary to secondary to tertiary amines depending upon the particular catalyst and the hydrogenation conditions being used. Typically, nitriles have been hydrogenated to primary or secondary amines using Raney nickel, Raney cobalt, supported nickel and supported cobalt catalysts. Rhodium catalysts have also been used to synthesize secondary amines from nitrile hydrogenation. But, due to the high cost of rhodium these catalysts may not be very practical. Representative patents illustrating the hydrogenation of nitriles to produce various amines and/or disproportionation of an amine containing feedstock are as follows:
U.S. Pat. No. 5,130,491 discloses a method for the production of secondary amines from fatty nitriles, e.g., tallow nitrile, utilizing a nickel catalyst promoted with copper, chromium or molybdenum. Secondary amine production is enhanced by hydrogenating the nitrile in a two-stage process with the second stage being carried out in the absence of ammonia. Temperatures range from 100.degree.-200.degree. C. while pressures range from 50-5000 psig.
U.S. Pat. No. 2,781,399 discloses a process for producing long-chain dialiphatic secondary amines as well as dialkyl and dialkylene amines as well as aromatic secondary amines and aromatic aliphatic secondary amines. The patent notes that the reaction to produce secondary amines is difficult to control and yet obtain a desired secondary amine product of good color and quality at acceptable reaction rates. The catalytic hydrogenation of the aliphatic nitrile is carried out using a nickel catalyst, preferably Raney nickel under anhydrous conditions. Alkali and alkaline earth metal hydroxides addition is undesirable where the feed source contains small amounts of free fatty acids.
U.S. Pat. No. 4,739,120 discloses a process for the hydrogenation of nitriles to primary amine using a rhodium catalyst. The reaction is carried out in the presence of a two phase solvent system comprising an aqueous phase and an immiscible organic phase.
U.S. Pat. No. 5,235,108 discloses a process for preparing secondary alkyl amines by the hydrogenation of alkyl nitriles using a nickel-containing catalyst-containing copper as a promoter. The patent suggests catalytic systems for the hydrogenation of nitriles which include catalyst components of nickel, copper and cobalt as well as dual systems, e.g., nickel-copper chromite and cobalt-copper chromite.
U.S. Pat. No. 3,177,258 discloses a process for the hydrogenation of unsaturated materials, such as unsaturated hydrocarbons and aliphatic and aromatic nitriles. The catalyst used for the hydrogenation is a ruthenium-containing catalyst combined with a platinum metal, e.g., ruthenium combined with platinum, palladium or rhodium. In the hydrogenation of propionitrile, coprecipitated and mixed metal ruthenium-platinum and ruthenium-palladium complexes gave substantial levels of tertiary amine while the ruthenium-rhodium catalyst composition gave high concentrations of secondary amines.
U.S. Pat. No. 3,673,251 discloses a cyclic process for producing mono, secondary and tertiary polyamines by continuously hydrogenating the nitrile in the presence of a hydrogenation catalyst such as cobalt, platinum, palladium, nickel and so forth.
U.S. Pat. No. 5,075,506 discloses a process for producing secondary amines by the hydrogenation of nitriles over a cobalt catalyst promoted with zirconium.
U.S. Pat. No. 2,165,515 discloses a process for the production of amines by the catalytic hydrogenation of nitriles using cobalt and cobalt promoted with barium or manganese.
An article, Hydrogenation of Nitriles, J. Volf and J. Posek; Studies in Surface Science & Catalysis, Volume 27, p.105-144, 1986 discloses the hydrogenation of nitriles using a variety of catalysts, e.g., nickel, cobalt, platinum, rhodium, ruthenium and palladium. The effect of these catalysts on product slate is also shown.